N = int(input())
c = str(input())

w = c.count("W")
r = c.count("R")

cnt = 0

for i in range(r):
    if c[i] == "W":
        cnt += 1

print(cnt) N = int(input()) N int(input()) int input() input c = str(input()) c str(input()) str input() input w = c.count("W") w c.count("W") c.count c count "W" r = c.count("R") r c.count("R") c.count c count "R" cnt = 0 cnt 0 for i in range(r):
    if c[i] == "W":
        cnt += 1 i range(r) range r if c[i] == "W":
        cnt += 1 c[i] == "W" c[i] c i "W" cnt += 1 cnt 1 print(cnt) print cnt N = int(input()) int(input()) N cnt = 0 0 cnt w = c.count("W") c.count("W") w cnt += 1 1 cnt c = str(input()) str(input()) c r = c.count("R") c.count("R") r
N = int(input())
c = str(input())

w = c.count("W")
r = c.count("R")

cnt = 0

for i in range(r):
    if c[i] == "W":
        cnt += 1

print(cnt)